Offset loop for wobble

ABSTRACT

An offset correction is automatically determined and routinely updated to reduce or eliminate data retrieval errors that may be caused by low level distortion in optical disc data storage recording, re-recording and retrieval system. An offset control loop is provided for reading information from a modulated wobble signal with which the data is recorded to an optical disc data storage medium to provide detection of an offset and correction of that offset to facilitate implementation of precise timing synchronization and/or encoded information contact in the system. The offset detector measures a wobble signal and mathematically converts detected information regarding the measured wobble signal to an offset correction by integrating the wobble signal over a specific time interval and comparing the integrated value to an expected integrated value. The integration may be performed over at least one period of the sinusoidal wobble signal, and the correction added to the wobble signal.

This is a Continuation of application Ser. No. 12/896,358, filed Oct. 1,2010, which is a Continuation of application Ser. No. 11/746,371, filedMay 9, 2007, which claims the benefit of U.S. Provisional PatentApplication No. 60/799,586, “OFFSET LOOP FOR WOBBLE,” filed on May 11,2006. The disclosure of the prior applications is hereby incorporated byreference herein in its entirety.

BACKGROUND

The systems and methods according to this disclosure are directed toreducing data recovery errors including low frequency distortions thatcan degrade the quality of timing loop information and/or detection ofaddress information in digital data recording systems, particularlythose in which data is recorded on recordable or re-recordable opticaldisc data storage media.

With a need to provide removable non-volatile data storage media onwhich increasing amounts of data can be recorded and/or re-recorded,optical disc data storage media have proven both comprehensive andflexible enough to support expanding data storage requirements. Opticaldisc data storage relates to placing data on a recordable, re-recordableand/or readable surface of an optical disc. In general, to record dataon, or recover data previously recorded on, an optical disc, a lightbeam is used to scan the surface of the optical disc using systemsspecifically designed for such data recovery. Currently-availablerecordable or re-recordable optical disc data storage media include:CD-R (Compact Disc-Recordable), DVD-R (Digital Video Disc-Recordable),DVD-RW (DVD-Rewritable), DVD+R (Writable Optical Disc), DVD+RW(Rewritable Optical Disc), DVD-RAM (DVD-Random Access Memory), and newtechnology higher density recordable or re-recordable optical datastorage discs known as BD technology, such as HD-DVD (High Density-DVDor High Definition-DVD) and Blu-ray Discs.

Differing methodologies are, therefore, required by which, when data isrecorded or re-recorded to such optical disc data storage media, atiming synchronization signal is provided, monitored and adjusted inorder that the readback, or data retrieval, system is cued to retrievethe discretely recorded or re-recorded data from a discrete portion ofthe disc at the precise speed with which the data was recorded.

A conventional optical disc formatted for land-groove recording is shownin exemplary embodiment in FIG. 1. Digital data is stored on suchoptical discs in the form of arrangements of data marks in spiraltracks. As shown in FIG. 1, grooves 100 and lands 110 are formed bymeans of a guide channel cut into the surface of a disc substrate. Arecording layer (not identified) is then formed over the entire discsurface including the surfaces of the grooves 100 and the lands 110. Thegrooves 100 and the lands 110 each form continuous recording tracks onthe disc. Data recording and reproducing are accomplished with such anoptical disc storage medium by scanning the groove recording track orthe land recording track with a focused light beam spot of an opticaldisc drive device, as shown in, and described in connection with, FIGS.2 and 3 below. It should be noted that, in some formats, data isrecorded both on lands and grooves. In other formats, data is recordedonly in the grooves.

FIG. 2 illustrates an exemplary conventional apparatus for implementinga process to write data to an optical disc data storage medium. As shownin FIG. 2, an input stream of digital information 200 is converted usingan encoding/modulating unit (encoder/modulator) 205 into a drive signal210 for a light source such as a laser source 220. The laser source 220emits a light beam 225 that is directed toward, and focused onto, arecording surface 250 of an optical disc data storage medium 245. Thefocusing of the light beam 225 typically involves an illumination opticsunit 230 to produce a very precise scanning spot 240. The diameter ofthe scanning spot 240 precisely coincides with the width of the grooveand/or the land in the optical disc data storage medium 245. In order toaccommodate more information on a single optical disc data storagemedium, the lands and the grooves are made individually thinner in aradial direction requiring that the illumination optics unit 230ever-more-precisely focus the scanning spot 240, thereby reducing thediameter of the scanning spot 240. As the surface 250 of optical discdata storage medium 245 is rotated under the scanning spot 240, energyfrom the scanning spot 240 is absorbed by a surface treatment on thesurface 250 of the optical disc data storage medium 245 through heatingof a small, localized region of the surface 250. The reflectiveproperties of the surface 250 of the optical disc data storage medium245 are thus locally discretely altered in accordance with, and toreflect recording of, the input data stream 200. Modulation of the lightbeam 225 is synchronous with the drive signal 210, so a circular trackof data marks is formed as newly written data 235 as the surface 250rotates.

FIG. 3 illustrates an exemplary conventional apparatus for implementinga process to read data from an optical disc data storage medium. Asshown in FIG. 3, a light beam 305 from a light source such as a lasersource 300 (which may be the same as the writing laser source 220 shownin FIG. 2) is directed through a beam splitter device 310 into anillumination optics unit 320 (which may be the same as illuminationoptics unit 230 shown in FIG. 2) to focus the light beam 305 onto asurface 340 of the recorded optical disc data storage medium 335. Aspreviously-recorded data marks to be read 345 pass under a scanning spot350, light is reflected toward the illumination optics unit 320.Reflected light is collected by the illumination optics unit 320 anddirected by the beam splitter 310 toward a collector of a data opticsunit 360. The data optics unit 360 converges the reflected light ontoone or more detectors in a light detector array 370. Detectors in thedetector array 370 convert the reflected light into a current modulatedsignal 375. This collected current modulated signal 375 is amplifiedand/or decoded in an amplifier/decoder unit 380 to produce an outputdata stream 385 that corresponds to the previously-recorded data marksto be read 345 from the surface 340 of the optical disc data storagemedium 335.

In data storage applications, inclusion of synchronizing marks, alsoreferred to as timing information marks, and physical locationinformation, are essential for recording data at a certain location onthe optical disc data storage medium to facilitate, among othercapabilities, finding the data location at a later time. A sectornumber, sector type and a land track/groove track can be recognized fromthe address information. In other words, the address informationprovides information for finding a specified sector to record/reproducedata to/from a certain location in an optical disc data storage medium.

When data is stored randomly on an optical disc data storage medium,various methods are included in the recording process to encode addressand timing synchronization information. One method includes recordingsuch information on, for example, a non-data area or non-recording areaof the optical disc data storage medium by forming embossed pitsseparately from data recording sectors. These pits are pre-formed andthen during the recording process recorded with non-data information tofacilitate data identification and location, and timing synchronizationfor readback. A drawback to this method, however, is that thesepre-pitted areas reduce the effective recording area of the optical discdata storage medium. Another method employed, particularly for higherdensity recording applications, is referred to as “wobbling” in whichthe lands and grooves of an optical disc data storage medium arepre-wobbled, in a radial direction, at a specific frequency.

FIG. 4 illustrates an exemplary embodiment of a conventional opticaldisc data storage medium 400 into which a predetermined reference wobble410 is physically encoded, i.e., the grooves (and/or lands) of therecordable surface of the optical disc data storage medium arephysically pre-wobbled at a given frequency. As shown in FIG. 4, asinusoidal wave with an amplitude in a radial direction is physicallyintroduced into the grooves. When data is recorded, frequency or phasemodulation is then performed around this reference wobble. The addressinformation is encoded in a modulated wobble signal, and introduced, forexample, with a measurable, modulated signal offset when the data isrecorded to the optical disc data storage medium 400. During readbackof, and/or other recovery of data from, the optical disc data storagemedium, an address of the pre-recorded data may be identified bydemodulating the recorded wobble signal from the reference wobble.Timing synchronization information for, for example, controllingrotation speed of the optical disc data storage medium precisely tofacilitate clear readback or data recovery may be implemented bydemodulating a modulated wobble signal in comparison to a wobblereference signal. Precise timing synchronization for readback and/orother data recovery is implemented through use of a timing loop such as,for example, a phase-locked loop to control a readback speed of datafrom a sector of the optical disc data storage medium in response to thedemodulated recorded wobble signal.

Errors in detecting and properly employing a wobble signal may beintroduced by, for example, presence of low frequency distortion and/ora DC-offset component in the wobble signal.

SUMMARY

Several conventional methods are employed to implement such a timingloop for speed control in such digital data recording and reproducingsystems, particularly those which read data to and read data fromoptical disc data storage media. The objective in such control is torecord or eliminate the likelihood of data retrieval errors. Inprecisely implementing timing control and/or detecting the wobbleaddress signal, it would be advantageous to find a simple methodology toreduce or otherwise eliminate low frequency distortion that may becaused by errors in precisely filtering information readback from theoptical disc data storage medium. Typically some form of offset loopfeedback mechanism is employed to provide an offset correction signal todetect and correct for such low level distortions during readback ofinformation pre-recorded on the optical disc data storage medium.

A simplified capability whereby an offset correction may beautomatically determined and routinely updated in order to reduce orotherwise eliminate low level distortion in optical disc data storagerecording, re-recording and retrieval systems is disclosed.

The systems and methods according to this disclosure may provide animproved offset timing loop for reading information from associatedmodulated wobble signals with which data is recorded to an optical discdata storage medium to provide detection of an offset error andcorrection for that offset error to facilitate precise implementation oftiming control and/or detecting the wobble address signal via theimproved offset control loop.

The systems and methods according to this disclosure may provide a noveloffset detector for measuring a DC-offset and mathematically convertinginformation regarding the measured offset to an offset correction toreduce or otherwise eliminate data retrieval errors particularly thosethat may be associated with low level distortion.

The systems and methods according to this disclosure may rely on thebasic sinusoidal nature of a wobble signal by integrating the wobbleover one complete period (T) of the sinusoidal signal and comparing theactual integrated value to an expected integrated value, generally zeroin the absence of any predetermined offset, to determine the detectedoffset, and to introduce offset correction through, for example, anoffset control unit, in some form of timing feedback loop.

In various exemplary embodiments, the systems and methods according tothis disclosure may provide varying capabilities whereby certainrecording or disc formats, in which deviations from zero occur inindividual wobble periods due to, for example, types of frequencymodulation used, to integrate the wobble signal over a plurality ofperiods and compare the integrated signal value for the plurality ofperiods to an expected value of zero, thereby generating an offsetsignal.

In various exemplary embodiments, the integrated result may be compared,as necessary, to a wobble signal which may contain a specific presetDC-offset and correction may be introduced to the preset DC-offset.

The proposed integration scheme may incorporate a time period differentfrom a single wobble period, as a timing window. Wobble signalinformation measured with, and integrated within, such a timing windowmay be combined with such information measured and integrated for aplurality of successive timing windows where the duration of the timingwindows is constant but is other than a complete wobble signal period,in order to detect the offset and generate a correction for the detectedoffset.

In various exemplary embodiments, an integration scheme may begin andend in any phase of a wobble period as long as the integration timespans one or more complete wobble periods, or one or more completetiming windows.

The proposed integration scheme may be performed over phased shiftboundaries. It should be recognized that such integration may result, inthe absence of a DC-offset, in temporarily providing a non-zero meanerror to the signals. If the integration is, however, performed overmultiple phase shift boundaries, the non-zero means of the error signalwould cancel each other out because a next phase transition boundary mayyield an error signal mean of approximately the same amplitude but withan opposite sign from the previous phase shift boundary. Such a resultwould also ensue for integrated results from a number of successivetiming windows in which the duration of the timing window is other thana full wobble period as described above.

In various exemplary embodiments the systems and methods according tothis disclosure may aggregate and/or average the integrated results froma plurality of wobble periods. This aggregated and/or average signalcorrection, may then be introduced into the offset timing loop only uponactuation of a specific actuating signal to the system, hereinafterreferred to as a “dump signal.”

These and other objects, advantages and features of the disclosedexemplary systems and methods are described in, or apparent from, thefollowing description of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will be described, in detail, with reference tothe accompanying drawings, where like numerals represent like parts, andin which:

FIG. 1 schematically illustrates, in magnified detail, an exemplaryembodiment of an optical disc data storage medium for land-grooverecording;

FIG. 2 illustrates an exemplary embodiment of a conventional apparatusfor implementing a process to write data to an optical disc data storagemedium;

FIG. 3 illustrates an exemplary embodiment of a conventional apparatusfor implementing a process to read data from an optical disc datastorage medium;

FIG. 4 illustrates an exemplary embodiment of an optical disc datastorage medium with a radially sinusoidal predetermined wobblephysically introduced into the lands and/or grooves of the optical discdata storage medium;

FIGS. 5A and 5B illustrate typical sinusoidal waves such as thoseintroduced into the lands and/or grooves of the optical disc datastorage medium shown in FIG. 4, and such a wave that is affected byDC-offset;

FIG. 6 schematically illustrates a first embodiment of an offset controlloop that may employ an offset detector according to this disclosure;

FIG. 7 schematically illustrates a second embodiment of an offsetcontrol loop that may employ an offset detector according to thisdisclosure;

FIG. 8 schematically illustrates an offset detector according to thesystems and methods of this disclosure that may be introduced intotypical embodiments of offset control loops such as those illustrated inFIGS. 6, 7, and 9;

FIG. 9 schematically illustrates a third embodiment of an offset controlloop including a dump signal for selectively introducing offset controlto the system, which may employ an offset detector according to thisdisclosure;

FIGS. 10 and 11 schematically illustrate first and second embodiments offilters that may be included in an offset control loop and coupled withan offset detector according to this disclosure; and

FIG. 12 is a flow diagram depicting an exemplary method for improvedoffset detection and timing synchronization signal error correctiongeneration according to this disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The following description of various exemplary embodiments of systemsand methods for implementing an improved offset loop for detecting anoffset by referencing a wobble signal according to this disclosure mayrefer to optical disc data storage media and systems and methods forrecording data on, and retrieving data from, such media for clarity andease of understanding. All references to such systems and media, such asthose shown in exemplary manner in FIGS. 1-4, are intended to beillustrative of environments to which systems and methods according tothis disclosure may be adapted. The systems and methods according tothis disclosure should not be construed, however, as being limited tosuch applications, or to any specific system that may be consideredlimited by the elements shown in the figures. An offset detectoraccording to the systems and methods of this disclosure may findapplicability in any system in which a typically sinusoidal wave may beused for, for example, timing synchronization and/or any manner ofidentification of information, and where precise timing synchronizationmay prove beneficial in reducing or otherwise eliminating errors in thefunctioning of such system by introducing a correction factor based onintegration of the available sinusoidal information within the system.

The systems and methods according to this disclosure provide acapability to extract information from recording tracks of a recordableand/or re-recordable optical disc data storage medium that are wobbledto assist, for example, with timing synchronization during recording,and/or to give address information, and to detect an offset correctionwhich can be input as an offset control to facilitate timingsynchronization and other benefits during playback. Such timingsynchronization and other benefits are designed to reduce and/oreliminate errors in data recovery from sources such as, for example, lowfrequency distortions in radial push-pull (RPP) signals within suchsystems.

Exemplary offset control loops are shown, for example, in FIGS. 6 and 7and may be provided in a system for recording data to, and/or readingdata from, an optical disc data storage medium to reduce data recordingor reproducing errors in data recording and reproducing systems. Asdiscussed briefly above, the recording track of an optical disc datastorage medium is wobbled as a sinusoid such that RPP signals form abasically sinusoidal waveform during data recovery, playback and/orreadback. Because low frequency distortions can degrade the ability toimplement, or otherwise degrade the quality of, timing synchronizationinformation and/or detection of address information, systems and methodsaccording to this disclosure provide improved methods for detecting lowfrequency distortions in the RPP signal. In various exemplaryembodiments, an RPP signal may be integrated over one or more wobbleperiods to obtain a mean value of the signal. The mean value of the RPPsignal may then be used, be calculated and fed back through an offsetloop to provide offset control of a wobble signal to reduce, or even toeliminate, low frequency distortion that may be introduced into readbackof data based on imprecision in system control.

According to a wobble signal method of data address and timingsynchronization, a predetermined wobble is physically introduced byvarying both walls of a groove in an optical disc data storage medium.This predetermined wobble may be used as an auxiliary clock signalduring recording.

Although the appearance of the optical discs is typically shown as aspiral configuration similar to FIG. 1, in actuality the grooves in thediscs to which the systems and methods according to this disclosure maybe directed, include this predetermined wobble in the form of a radiallysinusoidal wave. The wobble refers to a radially sinusoidal deviation ofthe groove track, as shown, for example, in FIG. 4. The groove is not asimple Archimedes Spiral, as shown in FIG. 1, rather it is “wobbled” ina sinusoidal fashion. During readback of the data stored on the opticaldisc data storage medium, a readback device such as that shown inconventional form in, for example, FIG. 3, just prior to, or coincidentwith, reading back the data stored on the disc may detect thepredetermined wobble from an unrecorded sector of the optical disc datastorage medium. The readback device employs this detected wobble to lockprecisely onto, for example, a pre-groove track, and to then initiallyset the timing synchronization for readback of data from aspecifically-addressed sector to which the readback device is directed.

FIG. 5A illustrates a typical sinusoidal wave such as that introducedinto the lands and/or the grooves of the optical disc shown in FIG. 4.Of note in FIG. 5A is that the wave is sinusoidally cyclic with a periodindicated in FIG. 5A as T.

A predetermined frequency or phase modulation is introduced in therecording medium. This frequency and/or phase modulation is capable ofbeing detected by the readback device. Differing methodologies havepreviously been employed to read (demodulate) this signal and to employthe demodulated signal to aid in identifying data, adjusting timingsynchronization or implementing other purposes.

FIG. 5B illustrates a wobble signal exhibiting a low-frequencydistortion (fluctuation) component and/or a DC-offset component to whichthe systems and methods according to this disclosure may be addressed.As shown in FIG. 5B, the wobble signal is not symmetric in amplitudeabout some preset level over several periods. Integrating this wobblesignal, for example, over one or more periods would result inidentification of a non-zero DC-offset. By subtracting such a determinedDC-offset from the raw wobble signal, a corrected wobble signal may bepresented to the various filters and/or phase-locked-loop circuits andsystems for retrieving information from, for example, optical disc datastorage media.

FIG. 6 schematically illustrates an offset control loop 600 that mayemploy an exemplary offset detector according to this disclosure. Ingeneral, in an offset control loop 600, the offset component is detectedby an offset detector 610 through a sampling procedure of, for example,a wobble signal. On the basis of the offset component thus detected, anoffset correcting signal is calculated and introduced via an offsetcontrol unit 620 to produce a signal that mediates or cancels out thedetected offset component.

An offset correction detected by the offset detector 610 and properlyconverted by the offset control unit 620 may be added at an adder 630 tothe input wobble signal w_(s) and the output signal passed to the systemwithin which the offset control loop is housed to better facilitatecontrol of timing synchronization in the system. The output signal maybe passed to the offset detector 610 generally continuously in orderthat a detected offset error signal is fed to the offset control unit620 to automatically and constantly update the offset correction signal.Employing such offset correction is desirable to reduce and/or otherwiseeliminate low frequency distortions that may lead to data readbackerrors. Offset control unit 620, such as that schematically illustratedin FIG. 6, may be but a single offset control block element for example,a low pass filter for filtering incoming error signals for low frequencycomponents or DC component. Typical filters for performing suchfunctions are shown in FIGS. 10 and 11. Inputs to, and outputs fromoffset control loops may be in a form of both analog and digitalsignals.

FIG. 7 schematically illustrates a second embodiment of an offsetcontrol loop 700 that may employ an offset detector according to thisdisclosure. In FIG. 7, an offset control loop 700 includes use of acorrection in an analog domain with an offset detector in the digitaldomain. It should be recognized and appreciated that analog to digitalconversion need not occur in the depicted portion of the circuit.Rather, differing offset control loops may deal with wobble signalinformation as either digital or analog data, any necessary conversionmay occur at other portions in the circuit.

The offset control loop 700 illustrated in FIG. 7 includes many of thesame features of the offset control loop shown in FIG. 6. These includean offset detector 710, offset control unit 720 and an adder 730. Offsetcontrol loop 700 also incorporates, however, an analog-to-digitalconverter (ADC) 740. With the inclusion of the ADC 740, wobble signalinputs are converted from analog to digital format for use in the offsetdetector 710 and offset control unit 720, and to be otherwise output tothe system from the offset control loop 700.

FIG. 8 schematically illustrates an offset detector according to thesystems and methods or this disclosure that may be introduced intotypical embodiments of offset control loops such as those illustrated inFIGS. 6, 7 and 9. The offset detector 800 shown in FIG. 8 can beincluded in either of the offset control loops 600 or 700, as elements610 or 710, as shown in FIGS. 6 and 7.

During playback and/or retrieval of information previously stored on thedisc, the wobble signal, as phase or frequency shifted, or not, can beused as a timing synchronization signal. The playback apparatusretrieves the basically sinusoidal (or cosine) wave with or withoutphase shifts, and with or without frequency shifts.

In various exemplary embodiments, the offset detector 800 shown in FIG.8 integrates the read wobble signal over one or more time intervals.Such time intervals may relate to a single or multiple sinusoidal waveperiods (T as shown in FIG. 5A) or may otherwise include any periodic,sequential time window of a specified time interval, which may not berelated to the sinusoidal period T of the wobble signal. Offsetdetection, as will be described in greater detail below, may beimplemented by integrating the detected wobble signal over the specifiedtime interval, i.e., one phase period T of the wobble signal, orotherwise in any timing window for sequentially integrating the wobblesignal. The integration may be synchronized with the phase of the wobblesignal over one or more periods of that signal. For many optical discformats, integrating the wobble over one period may yield an expectedvalue of zero. In such instances, any integrated result that is otherthan zero represents the detected offset. This detected offset may thenbe fed back through the offset control loop to the input wobble signaland the input wobble signal will then be corrected with this offset andoutput to the system within which the offset control loop is resident.Varying optical data disc storage media formats, with varying discrecording apparatus for recording information thereon, may yielddeviations from zero for individual wobble periods due to types ofmodulation, frequency or phase modulation, employed. Over multiplewobble periods, however, the mean for such an integration operationshould be zero. Again here, any non-zero integration result mayrepresent a detected offset to be added to input wobble signal prior tooutput. Several other variations of this basic concept may beimplemented. One such variation regards integration over wobble periodsfor systems which in some instances purposely generate a non-zeroDC-offset. For these systems, the integration result should be equal toa predetermined DC-offset, or compared to the predetermined DC-offset inorder to render a detected error.

In various exemplary embodiments, the systems and methods according tothis disclosure provide an offset detector 800 that integrates thewobble signal over at least one wobble period to get an estimate of acorrection signal, by using the following equation:

$\begin{matrix}{e_{t} = {\sum\limits_{T}^{\;}\;\omega_{s}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

A determination may need to be made whether to synchronize theintegration with the phase of the signal. For example, in cases wherethe data is encoded as phase shifts, the integration may besynchronized. If not, the integration may occur discretely orcontinuously over several cycles in order to nullify false errors thatmay be induced by, for example, interaction across a phase boundary.

FIG. 9 illustrates a third embodiment of an offset control loop 900including a “dump signal” for selectively introducing offset control tothe system which may employ an offset detector according to thisdisclosure. As shown in FIG. 9, the offset control loop 900 includes anoffset detector 910, an offset control unit 920 and an adder 930. Inthis regard, the offset control loop shown in FIG. 9 is similar to thoseshown in FIGS. 6 and 7. Offset detector 910 incorporates an integratorconsisting of an adder 902 and a memory element 904, a signal controlswitch or logic signal gate 906 to control when to output the integratedsignal and reset the integrator. In offset control loop 900, offsetdetection occurs with offset detector 910. A difference is thatintegration occurs, via integrator 904 and internal adder 902 withinoffset detector 910 based on the position of logic signal gate 906.Output from the offset detector 910 is inhibited and not allowed to passto the offset control unit 920 until a discrete “dump” signal isgenerated to close logic signal gate 906 to allow offset detectorinformation to pass to the offset control unit 920.

It should be appreciated that the wobble period, as shown in the examplein FIG. 5, may be specified according to an optical disc format. By wayof example, for CD-R and DVD-R(W) formats, the integration may begin andend in any phase of the wobble period, as long as the integration timespans one wobble period. Because the wobbles for these two formats aresinusoids with either constant frequency (DVD-R(W)) or frequencymodulated with small delta frequency (CD-R), exemplary embodimentsaccording to this disclosure may employ sliding interval window filtersof length equal to the wobble period.

It may be preferable not to integrate the wobble signal across phaseshift boundaries in such an embodiment because such integration would,in the absence of DC-offset, temporarily yield non-zero mean errorsignals. However, if the integration is performed over phase shiftboundaries, the non-zero mean of the error signals may cancel each otherbecause the next phase transition boundary would yield an error signalmean of opposite sign from the previous phase shift boundary. In otherwords, an average error over a plurality of integration periods, forexample, in integration periods covering eight wobble periods for whichthere might be a phase shift would be zero.

FIGS. 10 and 11 schematically illustrate first and second exemplaryembodiments of filters that may be included in offset control loops andcoupled with offset detectors according to this disclosure. FIG. 10illustrates an integrating loop filter. FIG. 11 illustrates aproportional, integral and differential loop filter.

It should be appreciated that, given the required inputs for detectionof a wobble signal, the processing outlined above with regard to theoffset detector and/or offset control unit may be implemented throughsoftware algorithms, hardware or firmware circuits, or any combinationof software, hardware and/or firmware detection control and/orprocessing elements.

FIG. 12 is a flow diagram depicting an exemplary method for improvedoffset detection and error correction using a wobble signal read from anoptical disc data storage medium. As shown in FIG. 12 operation of themethod begins at step S1000 and proceeds to step S1100.

In step S1100, a wobble signal is detected. Operation of the methodcontinues to step S1200.

In step S1200, a determination is made whether any offset correction haspreviously been calculated. If, in step S1200, a determination is madethat no offset correction has previously been calculated operation ofthe method continues directly to step S1400.

If, in step S1200, a determination is made that any offset correctionhas been calculated, operation of the method continues to step S1300.

In step S1300, any previously-calculated offset correction is added tothe wobble signal. Operation of the method continues to step S1400.

In step S1400, the wobble signal is integrated over one or morespecified time intervals. Thus, integration may occur discretely for asingle time interval as shown in step S1400. Operation of the methodoptionally continues to step S1500.

In step S1500, a determination is made whether a single time interval isadequate. If, in step S1500, a determination is made that a single timeinterval is not adequate, operation of the method may revert to stepS1300 where a first integrated value is added as an offset correction tothe wobble signal and further integration occurs over additionallyspecified time intervals.

If, in step S1500, a determination is made that a single time intervalis adequate or otherwise that the number of time intervals previouslysampled is now adequate, operation of the method continues to stepS1600.

In step S1600, a comparison of the integrated result is made to a presetlevel to determine an offset correction. Operation of the methodcontinues to step S1700.

In step S1700, an offset correction is implemented, for example, byinputting an offset correction circuit through an adder to a wobblesignal to produce a corrected wobble signal. Operation of the methodcontinues to step S1800.

In step S1800, a determination is made whether offset correction iscomplete. If in step S1800, a determination is made that offsetcorrection is not complete, operation of the method may revert to eitherstep S1200, or step S1300, and continue.

If in step S1800, a determination is made that offset correction iscomplete, operation of the method proceeds to step S1900.

In step S1900, corrected wobble signal data is passed to the system.Such passing may occur by an auxiliary dump signal, for example, beingmanually or automatically input to a signal gate to cause the correctedwobble signal to be passed to the system in a controlled manner, or maysimply be automatic. Additionally, the wobble signal although indicatedin this method as being corrected by a series of discrete steps, may becontinuously updated as individually identified steps in the methodoccur virtually simultaneously. Operation of the method continues tostep S2000 where operation of the method ceases.

It should be appreciated that the time intervals discussed, for example,in steps S1400 and S1500 may be a single period of a wobble signal.Other time intervals, as discussed above, however, may be implemented.

The foregoing detailed description of exemplary embodiments of systemsand methods for improved control of the wobble signal using anintegrating offset detector based on information provided by detectingthe wobble signal in, for example, an optical disc data storage mediumrecording, re-recording and/or reading device is meant to beillustrative, and in no way limiting. The above detailed description ofsystems and methods is not intended to be exhaustive or to limit thisdisclosure to any precise embodiment or feature disclosed. Modificationsand variations are possible in light of the above teaching. Thedescribed embodiments were chosen in order to clearly explain theprinciples of operation of the systems and methods according to thedisclosure and their practical application to enable others skilled inthe art to utilize various embodiments, potentially with variousmodifications, suited to a particular use contemplated.

1. An apparatus for generating an offset correction signal, comprising:an offset detector configured to detect a wobble signal from a datastorage medium and determine an error signal in the wobble signal; andan offset control configured to compare the determined error signal toan integrated preset level to generate an offset correction signal, theintegrated preset level determined by integrating the wobble signal overa plurality of time intervals.
 2. The apparatus of claim 1, wherein thedata storage medium is a recordable optical disc data storage medium. 3.The apparatus of claim 1, further comprising: a feedback loop formed bythe offset detector and offset control, the feedback loop configured toprovide an offset control of the wobble signal.
 4. The apparatus ofclaim 3, further comprising: an adder included in the feedback loop, theadder configured to add a previously generated offset correction signalto the wobble signal to generate an output signal.
 5. The apparatus ofclaim 1, further comprising: an analog-to-digital convertor configuredto convert the wobble signal in analog format to digital format.
 6. Theapparatus of claim 5, further comprising: a feedback loop formed by theanalog-to-digital convertor, offset detector, and offset control, thefeedback loop configured to provide an offset control of the wobblesignal.
 7. The apparatus of claim 6, further comprising: an adderincluded in the feedback loop, the adder configured to add a previouslygenerated offset correction signal to the wobble signal to generate anoutput signal.
 8. The apparatus of claim 7, wherein theanalog-to-digital convertor is coupled between the adder and the offsetdetector.
 9. The apparatus of claim 1, wherein the wobble signal isintegrated over a single complete period of the wobble signal and atleast one additional complete wobble period.
 10. The apparatus of claim9, wherein the integration of the wobble signal is based on a format ofthe data storage medium.
 11. A method, comprising: detecting a wobblesignal from a data storage medium; and comparing an error signal in thewobble signal to an integrated preset level to generate an offsetcorrection signal, the integrated preset level determined by integratingthe wobble signal over a plurality of time intervals.
 12. The method ofclaim 11, wherein an offset detector detects the wobble signal from thedata storage medium and determines the error signal in the wobblesignal.
 13. The method of claim 12, wherein an offset control comparesthe determined error signal to the integrated preset level to generatethe offset correction signal.
 14. The method of claim 13, furthercomprising: providing an offset control of the wobble signal by afeedback loop formed by the offset detector and offset control.
 15. Themethod of claim 11, further comprising: adding a previously generatedoffset correction signal to the wobble signal to generate an outputsignal.
 16. The method of claim 13, further comprising: converting thewobble signal in analog format to digital format.
 17. The method ofclaim 16, further comprising: providing an offset control of the wobblesignal by a feedback loop formed by an analog-to-digital convertor thatperforms the converting, the offset detector, and the offset control.18. The method of claim 17, wherein the feedback loop includes an adderconfigured to add previously generated offset correction signal to thewobble signal to generate an output signal.
 19. The method of claim 11,further comprising integrating the wobble signal over at least oneadditional complete wobble period.
 20. The method of claim 19, whereinthe wobble signal is integrated over a single complete period of thewobble signal and the at least one additional complete wobble periodbased on a format of the data storage medium.